please help me i have only 15min

For each of the following statements, either prove true, or give a counter example (a) Given infinite languages L4 and L0L4L4 if L4 is nos a CFL then L9 is nok a CFL. (b) Given infinite languages L2 and L2,L7L0 if L2 is not a CFL thee L4 is nos a CFL (c) Given infinite languages L2 and L2,L1L2 if L1 is a CFL. then L2 is a CrL. (d) Given infinite languages L2 and L2L1L2 if L2 is a CFL. then L2 is a CFL