Show that the amount of coal used on the fifth trip is 1.624 tonnes, correct to 4 significant figures.
There are 39 tonnes of coal available. An engineer wishes to calculate \(N\), the total number of trips possible. Show that \(N\) satisfies the inequality
$$1.02 ^ { N } \leqslant 1.52$$
Hence, by using logarithms, find the greatest number of trips possible.