Question

Since when is 5^7 =8125?
if a number is a multple of ten, that means the last digit is zero. The leading digit cannot be zero.
9*10^5*1
on c, again, the leading digit cannot be zero.
d is right
e. no leading zero is allowed. 9*9*8*7*6*5*4= ?

can someone correct this for me parts A-E and if i am wrong can you help me....please

How many 7-digit telephone numbers are possible if the first digit cannot be zero and.....
a) only odd digits may be used?
5^7= 8125
my answer: 8125

b) the telephone number must be multiple of 10(that is , it must end in zero)?

10^6*1=1,000,000

my answer: 1,000,000

c) the telephone number must be a multiple of 100?

10^5*1*1=100,000

my answer 100,000

d) the first 3 digits are 481?

1*1*!*10^4=10,000

my answer 10,000

e) no repetitions are allowd?

10 combination 7 = 120

my answer: 120

oops for the part a: 5^7 = 78125

part e: 544320

i need help with c