There are 2000 households in Happy Valley, distributed across 20 districts. Five districts were sampled with replacement, with each random draw weighting a district in proportion to the number of households it contains. By luck, no district was selected more than once. Within each selected district, a simple random sample of 10% of the district's households was taken. Let $H$ be the number of households in a district, and let $C$ be the total number of cars owned by residents of those households sampled in the district. The five observed values of $(H,C)$ are (, ), (, ), (, ), (, ) and (, ).

(a) Give an estimate of the total number of cars owned by Happy Valley residents. Report your answer to the nearest integer.

(b) Give a standard error to accompany your estimate. Report your answer to the nearest integer.