Tax-rate is relevant and important for calculation of specific cost of capital of: ?

<p style="text-align:justify;"><strong><span>(a) Equity Share Capital,</span></strong></p> <p style="text-align:justify;"><strong><span>(b) Preference Share Capital,</span></strong></p> <p style="text-align:justify;"><strong><span>(c) Debentures,</span></strong></p> <p style="text-align:justify;"><strong><span>(d) (a) and (b) above.</span></strong></p>