1.A grocery store has 5 checkout counters, and 7 clerks. How many different ways can the clerks be assigned to the counters?

2.In how many ways can 3 English, 3 history, and 2 math books be set on a shelf?

3.In how many ways can those same 3 English, 3 history, and 2 math books be set on a shelf, if they are grouped by subject?

4.How many different 4-letter North American radio station call signs (like CKUL, KNBC, WCBS, and XTHO) can be made if the first letter must be C or K or W or X and none of the letters may be repeated?