The maximum kinetic energy of photoelectron liberated from the surface of lithium (work function =2.35V) by electromagnetic radiation whose electric component varies with time as E = a[1+cos (21 fit)] cos (27f2t) where 'a' is a constant, fi = 3.6x10' Hz and f2=1.2x10' Hz is [Take : h=6.6x10-34 J-s]
A. 2.6ev
B. 7.55eV
C. 12.5eV
D. 17.45eV