Answer:
4) M=5
Step-by-step explanation:
When multiplying exponents, you add them. When raising an exponent to another power, you multiply them.
(x^5*x²)³=(x^7)³=x^21
We can not see the rest of 12
To find this answer, we need to multiply 3.57 by 12.

Therefore, 12 planks will cost $42.84.