A function f(x)=x2+bx+cf(x) = x^2 + bx + cf(x)=x2+bx+c has the property that f(x)<0f(x) < 0f(x)<0 only for x∈(3,7)x \in (3, 7)x∈(3,7). Determine the value of b+cb + cb+c.
10
21
-11
31