Naira's Nightmare. On Friday, June $17,2016,$ the Central Bank of Nigeria $($CBN$)$ abandoned the Nigerian naira's $($NGN or N$)$ fixed exchange rate and allowed the currency to float. Previously fixed against the U$.$S$.$ dollar at NGN$196\mathrm{.}17=$ USD$1\mathrm{.}00,$ the naira closed at NGN$281\mathrm{.}71=$ USD$1\mathrm{.}00$ on Monday, June $20,$ the first day of trading following the float. The naira quickly floated $($sunk$)$ to NGN$324\mathrm{.}13$ by August $18.$ Similarly, the naira fell from NGN$221\mathrm{.}5772=$ EUR$1\mathrm{.}00$ to NGN$317\mathrm{.}5397=$ EUR$1\mathrm{.}00$ on June $20,$ and NGN$347\mathrm{.}0117$ on August $18.$

a$.$ What was the percentage change in the value of the Nigerian naira versus the dollar the first trading day?

b$.$ What was the percentage change in the value of the naira versus the dollar by August $18,2016?$

c$.$ What was the percentage change in the value of the Nigerian naira verus the euro the first trading day?

d$.$ What was the percentage change in the value of the naira versus the euro by August $18,2016?$