Graph please

The graph of  \(y=f'(x)=mx^2+nx+k\)   passes through the points  \(P({1 \over3};0), Q(1;0) \ and \ R(0;1)\)

 

Determine the values of m, n and k....I have posted this before, but cancelled it because I thought I had won it, however, I just realised that's not the case..sorry about this..At least I know k is 1......lol..Thank you all very much.