Probability density function

i have the following pdf which relates to X square ft of a (round) pizza

f(x)= 6(x-x^2) for 0 < x < 1

0 elsewhere

i had to find the mean and variance which i got as 0.5 and 0.05 respectivly

now i have been asked to find the proportion of pizzas that wont fit in a box of size 1ft square

the pizzas are circular so i found the maximum size of pizza that would fit in the box which is 0.25pi so i need to find the are of the graph which is above that value the trouble is integrating between these two values just gives me a silly answer so i know i am doing something wrong i just cant place what (by silly answer i mean negative)