Answer all the questions and plot a graph.

From the previous calculation, the MTTF is $\boxed{\text{25000 hr}}$.
The reliability values $R(t) = e^{-\lambda t}$ at the given times are:

To plot the reliability attenuation curve:

• The x-axis represents Time (hr). It should range from 0 to at least 50000 hr.
• The y-axis represents Reliability $R(t)$. It should range from 0 to 1.

• Plot the points from the table, with time on the x-axis and reliability on the y-axis. For example, plot (5000, 0.8187), (10000, 0.6703), and so on.
• At time $t=0$, the reliability is $R(0) = e^0 = 1$. So, the curve starts at the point (0, 1).
• Connect these plotted points with a smooth curve. The resulting graph will be an exponential decay curve. It will start at 1 on the y-axis and continuously decrease as time increases on the x-axis, approaching 0 but never quite reaching it. The curve will pass through the point $(25000 \text{ hr}, 0.3679)$, which corresponds to the MTTF where reliability is $e^{-1}$.