Let's say "m" is the manufactoring cost per drill (in dollars).
Then the manufactorer sells it for $4 more, so this would be:
m+4
Then the chain store sells it for 140% of the price is paid the manufactorer, so this would be "140% of (m+4)" which translates to "1.4•(m+4)" or more simply:
1.4(m+4)
P(m) = 1.4(m+4), where m is the initial manufactoring cost (in dollars).
Simplifying, you could rewrite this as:
P(m) = 1.4m + 5.6
