The insurance company offers full insurance against the potential loss of $(y z) from rain at a

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The insurance company offers full insurance against the potential loss of $(y z) from rain at a premium of $M, but the organizer may decide against full coverage by paying only a fraction f of the full premium. This means that she pays $Mf before the event, and the insurance company repays $0 if it is sunny and $(y z) f if it rains. (Keep things simple by not making the realistic assumption that f is restricted to the range 0 f 1.) What is the insurance companys dollar expectation if she buys full insurance?