Given that the rates of breakdown of Benzocaine, a local anaesthetic are 16 x 10 second 15 10-8 sec at 30°C and 25°c respectively. Compute the shelf-life of an ampoule (Injection) of the
drug stored in the fridge at 5°C if the compendia provided a preparation of the drug shall contain
not less than 80% of benzocaine.

You need to figure out at which x-value does the graph has a tangent line slope of -1.remember, the derivative is the slope of the tangent line. so find the derivative function and set it to equal -1 to find the x-value that will have a tangent line slope of 0.differentiate with the chain rule.    set the derivative to equal -1 and solve for x.      take log base 10 of both sides. also recall that  .    so the x-coord of the point of tangency is .the y-coordinate of this point of tangency can be calculated using the original function:     using point-slope form, the equation of the tangent line is      the x-intercept of this tangent line is when the graph is at y=0.    this rounds off to  .choice c.