Just (a), (b) and (c) please

4. In each case, sketch the region whose area is represented by the limit of the Riemann sum. Express lim S,, as a definite integral and find its value by using the Fundamental Theorem of Calculus. a. S, = ( #)AX, OSXSI * = 3k) 2 b. S, = -1+ Ax , - 15x52 n c. S, = 1 2 (k - 1) Ax, 15x53 n d. S, = Ax, 15x52 k = 1 + n 2 cos TT 3kTT e. S, = + = Lx, SXS K= 1 f. S, = in2 Ax, OSxSIn2 k =