Looks easy but isn't. Solve properly in white paper, blue pen. HANDWRITTEN

Aggregate annual claims from a portfolio of general insurance policies have a compound Poisson distribution with Poisson parameter 20. Individual claim amounts have a uniform distribution over the interval (0,200). Excess of loss reinsurance is arranged so that the expected amount paid by the insurer on any claim is 50. Calculate the variance of the aggregate annual claims paid by the insurer