Solve the following using Calculus methods: a. [10 marks] A radioactive decay diminishes the quantity M() of a material to half its original quantity No in 15 hours. How long will it be before it decays by 90% of its initial quantity? Hint: N(t) = No e-kt b. [6 marks] A bird is flying horizontally at a height 110 m and at a rate of 10 m/min passes directly over a pond. How fast is its straight-line distance from the pond increasing 15 minutes later