Sam used 2.50 m of blue nylon and 1.50 m of yellow nylon to decorate his poster. The price per metre was the same for each colour. He paid $9.75 for the yellow nylon.
How much did he pay for all the nylon?

List x1, x2, x3, x4 where xi is the left endpoint of the four equal intervals used to estimate the area under the curve of f(x) between x = 4 and x = 6. a 4, 4.5, 5, 5.5 b 4.5, 5, 5.5, 6 c 4.25, 4.75, 5.25, 5.75 d 4, 4.2, 5.4, 6