https://foxoyo.com/mcq/80649/9-engines-consume-24-metric-tonnes-of-coal-when-each-is-working-8-hours-in-a-day-how-much-coal-is-required-for-8-engines-each-running-13-hours-a-day-if-3-engines-of-former-type-consume-as-much-as-4-engines-of-later-type