R(t)=85 t-2 t**2; t=4

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Holy FORTRAN, Batman!

R(4) = 85*4 - 2*4^2
= 340 - 32
= 308

To find the value of R(t) when t = 4, you need to substitute the value of t into the given equation. Let's go step by step:

Step 1: Start with the given equation R(t) = 85t - 2t^2.
Step 2: Replace t with the value 4 in the equation.
R(4) = 85*(4) - 2*(4)^2.
Step 3: Simplify the equation.
R(4) = 340 - 2*16.
R(4) = 340 - 32.
R(4) = 308.

Therefore, when t = 4, the value of R(t) is 308.