1.if n and p are different positive prime numbers,which of the integers n^4,p^3,and np has(have) exactly 4 positive divi

1.if n and p are different positive prime numbers,which of the integers n^4,p^3,and np has(have) exactly 4 positive divisors?
a,n^4 only
b,p^3only
c,np only
d,n^4 and np
e,p^3 and np
2.in a certain coding scheme,each word is encoded by replacing each letter in the word with another letter,the same code is used for all words,so that the same letter replaces a given letter each time the given letter occurs.what code will result when the word TAME is encoded by this scheme?
(1)when the word MAT is encoded,the result is DLX.
(2)when the word TEA is encoded,the result is XRL.
3.150,200,250,which of the following could be the median of the 4integers listed above?
答案给的是175和215（175我算出来了,但是没算出来215,算出来的是225,是在是脑袋疼,还是题弄错了~十分感谢了）