Question 11The numeral $47$ in base $a$ represents the same number as $74$ in base $b.$ Assuming both bases are positive integers, the least possible value of $a+b,$ written as a Roman numeral, is:$\mathrm{XIII}$$\mathrm{XV}$$\mathrm{XXI}$$\mathrm{XXIV}$$\mathrm{XVI}$