Please help with this algorithm question. Thanks

We have n requests (intervals) labeled 1,2,... ,n, with each requesti specifying a start time si and a finish time fi. Each interval i also has a value, or weight vi. Two intervals are compatible if they do not overlap. The goal of our problem is to select a subset S C 1,,n} of mutually compatible intervals, so as to maximize the sunn of the values of the selected intervals, ?cs vi