Answer:
Step 1: Finding r using the formula ln 2/h
[tex]1.\ r=\frac{ln\ 2}{h}\\ r=\frac{ln\ 2}{140}\\r=0.00495[/tex]
Step 2: Substitute the values in given formula
[tex]2.\ m_t=m_0e^{-rt}\\200=300e^{-0.00495t}[/tex]
Step 3: Divide both sides by 300
[tex]\frac{2}{3} =e^{-0.00495t}[/tex]
Step 4: Take the natural logarithm on both sides
[tex]ln\ \frac{2}{3} =ln\ e^{0.00495t}[/tex]
Step 5: Simplify
[tex]-0.405 = -0.00495t[/tex]
Step 6: Divide both sides by 0.00495
[tex]\frac{-0.405}{-0.00495} =t[/tex]
Step 7: Simplify
[tex]t=81.8\ days[/tex]
