The Department of Transportation (DOT) monitors sealed bids for new road construction. For new access roads in a certain state, let low bid (thousands of dollars) and let estimate of fair cost of building the road (thousands of dollars). The joint probability density of X and Y is f(x, y)= e^-y/10/10y 0< y

Complete Question

The complete question is shown on the first and second uploaded image

The  marginal density function of Y is  

The distribution is exponential distribution

and the expected value is

Step-by-step explanation:

From the question we are told that the function is  

Now the marginal density function of Y i.e f(y) is mathematically evaluated by obtaining the probability density function of y as follows

The distribution of the function above is exponential distribution with a rate parameter equals to  

  The mean DOT estimate E{Y} is mathematically evaluated as

    substituting value

-18 degrees is the answer : )

b

step-by-step explanation:

a difference is the result of subtraction. while each of these expressions has subtraction in it, a difference will be the result when subtraction is the last operation applied in the order of operations for the expression. this means subtraction must be outside of the parenthesis. only b has this.