ID#4143 BCS Mental ability Preli (42)

\text{Initial Bill } (P) = 420 \text{ BDT} \\
\text{After 12 months (10\% increase):} \\
B_{12} = P \times (1 + 0.10) = 420 \times 1.1 = 462 \text{ BDT} \\
\\
\text{After 18 months (Additional 20\% increase on } B_{12}): \\
B_{18} = B_{12} \times (1 + 0.20) = 462 \times 1.2 = 554.4 \text{ BDT} \\
\\
\therefore \text{Final Bill} = 554.4 \text{ BDT}