5x + 10 f (t ) = x2 + 4x + 4 where t is measured in years and f(t) in kilograms per year. Consider the integral 5x + 10 dx 12 x2+ 4x + 4 After substitution into u, the new integral can be written A Ja u -du (a) The value of A is K Ox + 2 O 5x 0 5 O 10 O 5x + 2 O 2.5 O x (b) The upper limit of integration b is 0 72 0 2 0 5 36 O -36 O 16 O -16 O 32