Although discount factors are given in the exam up to 20% it is a fairly easy equation to work out what the discount factor is. 1/(1+df%)n where n=number of years
(sorry there is no option to super/subscript, so n is to the power of) hope you understand
ie: 10% discount factors= so 25% discount factors
1/1.1 =0.909 1/1.25 =0.800 1/1.1squared =0.826 1/1.25 squared =0.640 1/1.1 to the power of 3=0.751 1/1.25 to power 3 =0.512