please help me with these two i am confused

6 If the substitution u = x2 - 4 is used on the definite integral f(x) dx, the new limits of integration are OA. U = 0 and u = -4. OB. u = 0 and u = 6. Oc. u = -4 and u = 32. OD. u = -4 and u = 6.Question 22 N The sum sin + N N represents the Riemann sum RN for which integral? j=1 47 /3 OA. sin(x) dx IT / 3 OB. sin(x) x dx oc. sin(x) dx TT /3 OD. sin(x) dx 47 /3 OE. sin(x) r dx T / 3 .71 / 2 OF . sin(x) dr J T. / 3