What section of PDA 1988 provides that it is impossible for patent to be renewed more than the third time

What section of PDA 1988 provides that it is impossible for patent to be renewed more than the third time

s. 6 (2) of the PDA1988

s.8 (1) of the PDAn1988

s.2(2) of the PDA1988

—>> s. 9 (2) of the PDA1988