A thermometer initially at $100^{ \circ}C$ is dipped at $t = 0$ into an oil bath, maintained at $150^{\circ}C$. If the recorded temperature is $130^{\circ}C$ after $1$ minute, then the constant of thermometer (in min) is

1. $1.98$
2. $1.35$
3. $1.26$
4. $1.09$

Answer: