(d) Bromthymol blue, an indicator with Ka value of 1.0x10-7, is yellow in ts HIn form and blue in its In-form. Suppose we put a few drops of this indicator in a strongly acidic solution. If the solution is then titrated with NaOH, at what pH will the indicator colour first be visible. Also show how it changes in the titration of a base, at what pH does the colour change?