I need help with this please :)

C

Step-by-step explanation:

this is an arithmetic sequence (we add something from element to element).

"an" describes the salary during the nth year.

a1 = $3000

a2 = a1 + 600

a3 = a2 + 600 = a1 + 600 + 600 = a1 + (3-1)×600

an = a1 + (n-1)×600 = 3000 + (n-1)×600

so,

a15 = 3000 + (15-1)×600 = 3000 + 14×600 = $11400

i think it is

step-by-step explanation:

a formal letter is a letter the you would send to a king