Let P(x)=x⁶+ax⁵+bx⁴+cx³+dx²+ex+f be a polynomial such that P(1)=1,P(2)=2,P(3)=3,P(4)=4,P(5)=5 and P(6)=6, then find the value of P(7).
a. 727
b. 729
c. 719
d. 720