## To find the formula for C as a function of I, we can use the two given points (C, I) and the formula for a linear function, y = mx + b.

Using the points (3839, 6650) and (5494, 4215), we can find the equation of the line:

First, calculate the slope, m:

m = (I2 - I1) / (C2 - C1)

= (4215 - 6650) / (5494 - 3839)

= -2435 / 1655

â‰ˆ -1.471

Now, let's substitute one of the points into the equation y = mx + b and solve for b:

6650 = (-1.471)(3839) + b

b = 6650 + 1.471(3839)

b â‰ˆ 6650 + 5643

b â‰ˆ 12293

Therefore, the equation for C as a function of I is given by:

C = -1.471I + 12293

To find the marginal propensity to consume (MPC) for the United States from 1990-1997, we need to determine the slope of the linear function, which is the coefficient of I in the equation.

From the equation C = -1.471I + 12293, we can see that the coefficient of I is -1.471. This value represents the MPC.

Thus, the marginal propensity to consume for the United States from 1990-1997 is approximately -1.471.