A curve y = f(x) passing through the point (1,2) satisfies the differential equation $x{dy\over dx}+y=bx^4$ such that $\int\limits_1^2f(y)dy={62\over5}$. The value of b is

(1) 10

(2) 11

(3) $32\over5$

(4) $62\over5$

(1) 10

(2) 11

(3) $32\over5$

(4) $62\over5$