A radioactive isotope has an initial mass of 10g. After 5years its mass has decreased to 7.5g.
a. (i) Formulate the differential equation governing the mass N(t) of the isotope at time t years, defining all symbols used.
b. (ii) Using the given data, determine the decay constant λ correct to four decimal places.
c. (iii) Find the half-life of the isotope, giving your answer to two decimal places.
d. (iv) How much of the isotope will remain after 20years? Express your answer correct to one decimal place.