If the sum of 5 consecutive positive multiples of a prime number is 105, what is the sum of the first 5 positive multipl

Let the prime number = p and multiple = m
Sum of 5 consecutive positive multiples of p = 105
=> (p * m) + [p * (m+1)] + [p * (m+2)] + [p * (m+3)] + [p * (m+4)]
=> pm + pm+p + pm+2p + pm+3p + pm+4p
$$=>5pm+10p=105$$
$$=>\frac{5p\left(m+2\right)}{5}=\frac{105}{5}$$
$$=>p\left(m+2\right)=21$$
This equation has 2 unknown variables which cannot be evaluated with 1 equation so the answer to the question cannot be determined

Answer = E