A sample of a reinsurer's payments made under a proportional reinsurance arrangement consists of the following values, in units of thousands of pounds: 4.5, 6.8, 22.9, 1.4, 3.8, 10.2, 19.4, 32.1 If the original claim amounts are modelled using a Gamma (a,1) distribution, and the retained proportion is 80%, find the distribution of the reinsurer's claims and hence estimate the parameters a and using a method of moments approach.