PHP多维数组求和

Array ( [图书楼] => Array ( [0] => Array ( [serial_number] => 51907180020053 [power] => 111.92 )

        [1] => Array
            (
                [serial_number] => 11908061080007
                [power] => 152.24
            )

        [2] => Array
            (
                [serial_number] => 51907180020042
                [power] => 
            )

        [3] => Array
            (
                [serial_number] => 51907180020053
                [power] => 111.92
            )

        [4] => Array
            (
                [serial_number] => 51907180020079
                [power] => 8.91
            )

        [5] => Array
            (
                [serial_number] => 51907180020097
                [power] => 
            )

    )
[女生宿舍] => Array
    (
        [0] => Array
            (
                [serial_number] => 51907180020046
                [power] => 0.01
            )

    )
[男生宿舍] => Array
    (
        [0] => Array
            (
                [serial_number] => 51907180020061
                [power] => 
            )

    )
[东侧家属院一单元] => Array
    (
        [0] => Array
            (
                [serial_number] => 11908061080017
                [power] => 177.21
            )

    )
[东侧家属院二单元] => Array
    (
        [0] => Array
            (
                [serial_number] => 11908061080015
                [power] => 111.04
            )

    )
[东侧家属院三单元] => Array
    (
        [0] => Array
            (
                [serial_number] => 11908061080018
                [power] => 86.53
            )

    )
[西侧家属院一单元] => Array
    (
        [0] => Array
            (
                [serial_number] => 11908061080005
                [power] => 121.20
            )

    )
[西侧家属院二单元] => Array
    (
        [0] => Array
            (
                [serial_number] => 11908061080011
                [power] => 138.85
            )

    )
[西侧家属院三单元] => Array
    (
        [0] => Array
            (
                [serial_number] => 11908061080014
                [power] => 59.27
            )

    )
[家属院一单元] => Array
    (
        [0] => Array
            (
                [serial_number] => 11908061080010
                [power] => 105.90
            )

    )
[家属院二单元] => Array
    (
    )
[家属院三单元] => Array
    (
        [0] => Array
            (
                [serial_number] => 11908061080002
                [power] => 104.10
            )
    )
[家属院] => Array
    (
        [0] => Array
            (
                [serial_number] => 11908061080006
                [power] => 96.64
            )

    )
[餐厅] => Array
    (
        [0] => Array
            (
                [serial_number] => 51907180020067
                [power] => 
            )

        [1] => Array
            (
                [serial_number] => 51907180020076
                [power] => 
            )
    )

)、

我想得到图书楼，女生宿舍，每个健名下面的power的总和，然后让健名比如图书楼后的值直接是总和，小弟不才，这个循环不知道该咋写，求大佬指教