please solve and explain these 4 questions step by step, thanks!

The cost of a structure is a combination of the cost of the foundation (k=$100,000&=15,000), columns (C=$75,000&c=10,000), beams (B=$90,000&B=12,000) and slabs (s=$150,000& s=20,000). If all cost components are normally distributed, determine the probability of the actual cost being between $400,000 and $450,000. Problem\#8: A company that operates taxis in a big city has purchased 20 new cars for $450,000. Each car has an expected life of 8 years and estimated salvage value of $5,000. Use the double declining balance method to determine the depreciation and book value for each year. ProblemH9: An engineering firm wants to invest money in order to accumulate $20 million in 8 years. How much should their equal annual instaliments be if the annual real interest rate is 5% and the inflation rate is 2% ? ProblemH10: A marble tile making plant has fixed costs of $150,000 per month. The variable costs per unit: (1) $2.2 for direct material, (2) $4.0 for direct labor, and (3) $0.8 for energy usage. How many units need to be sold annually to break even if the selling price of each unit is $10