HEL How many different 5-letter radio station call letters can be made if
a) The first letter must be H or P and no letter may be repeated?
b) Repeats are allowed, but the first letter is H or P
c) The first letter is H or P, there are no repeats, and the last letter is B ?
ILL GIVE BRAINLIEST if u can get it right and show work

Solve the system of equations. y= 2x y= x^2 - 15

The function a represents the cost of manufacturing product a, in hundreds of dollars, and the function b represents the cost of manufacturing product b, in hundreds of dollars. a(t) = 5t + 2 b(t) = 7t - 2t +4 find the expression that describes the total cost of manufacturing both products, a(t) + b(t). a. 7t^2 - 7t + 2 b. 7t^2 + 3 +6 c. 7t^2 + 7t - 6 d. 7t^2 - 3t + 6

Ineed to know the answer right now! !