Engineering Economy please solve all the problems with the correct concept step by step write the answer here so I can copy it

Problem 3 According to Descartes' rule of signs, determine the possible number of i values for the net cash flow series with the following signs: a) b) c) d) +++++ Problem 4 A manufacturing company has the net cash flows below. (a) Determine the number of possible rate of return values, and (b) Find all rate of return values between 50% and 120%. Problem 5 Consider a new automated production line that costs $125,428. Find rate of return per quarter if the quarterly operating cost is $7,000 and quarterly revenue is $15,000 over 5 years. Problem 6 What is the face value of a municipal bond that matures in 20 years and has a bond coupon rate of 6% per year with semiannual payments of $900 ? Problem 7 A mortgage bond is offered for sale at $6,000. The bond has a face value of $10,000 with a coupon rate of 8% per year, payable quarterly and has a maturity date after 18 years. There will be no dividend for the next 2 years and after that (for the following 5 years) there will be bond dividends. What rate of return will be realized if the bond was sold at year 7 for $7,000 (a) per quarter and (b) per year (nominal)