Choose the correct simplification of the expression a^6•b^3/a^4•b^2

Answer choices:
a^2/b
a^10•b^5
a^10/b^5
a^2•b

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