$70 \, cal$ of heat are required to raise the temperature of $2 \, moles$ of an ideal gas at constant pressure from $30^{\circ}C$ to $35^{\circ}C$. The amount of heat required to raise the temperature of the same gas through the same range ($30^{\circ}C$ to $35^{\circ}C$) at constant volume is ..... $cal$ $(R = 2 \, cal/mol \cdot K)$.

• A
  $30$
• B
  $50$
• C
  $70$
• D
  $90$