An article on estimating 28-day strength of concrete considered regressing y = 28-day standard-cured strength (psi) against x = accelerated strength (psi). Suppose the equation...

An article on estimating 28-day strength of concrete considered regressing y = 28-day standard-cured strength (psi) against x = accelerated strength (psi). Suppose the equation of the true regression line is y = 1830 + 1.4x.

(a) What is the expected value of 28-day strength when accelerated strength = 2420?
[removed] psi

(b) By how much can we expect 28-day strength to change when accelerated strength increases by 1 psi?
[removed] psi

(c) By how much can we expect 28-day strength to change when accelerated strength increases by 50 psi?
[removed] psi

(d) By how much can we expect 28-day strength to change when accelerated strength decreases by 50 psi?
[removed] psi