a$)$ The interest rate on a $$1,900,000$ mortgage is $5\%$ and has a $25-$year repayment period. What is the monthly instalment and the yearly instalment? $[3]$ b$)$ An asset costs $$100,000$ and has a salvage value of $$10,000.$ If the asset has a useful life of $4$ years, calculate the book value for each of the years using the following depreciation methods: i$.$ Straight$-$line method $[3]$ ii$.$ Declining balance method $[4]$