title: come up with a python code to solve the following problem
body: <p>Suppose the coverprice of a book is $24.95, but book stores get a 40% discount. Shipping costs $3 for the ﬁrst copy and 75 cents for each additional copy. What is the total wholesale cost for 60 copies? </p>
  
  <p>This is what i have tried:</p>
  
  <pre class="lang-py prettyprint-override"><code>    a='coverprice'
      &gt;&gt;&gt; b='discount'
      &gt;&gt;&gt; c='shipping costs'
      &gt;&gt;&gt; d='additional copies'
      &gt;&gt;&gt; e='no. of copies'
      &gt;&gt;&gt; a=24.95
      &gt;&gt;&gt; b=0.4
      &gt;&gt;&gt; c=3
      &gt;&gt;&gt; d=0.75*59
      &gt;&gt;&gt; e=60
      &gt;&gt;&gt; print ('total costs=',c+d)
      total costs= 47.25
      &gt;&gt;&gt; f='total cost'
      &gt;&gt;&gt; print ('total discount=',b*a)
      total discount= 9.98
      &gt;&gt;&gt; g='total discount'
      &gt;&gt;&gt; print('total purchase cost before discount=',a*e)
      total purchase cost before discount= 1497.0
      &gt;&gt;&gt; h='total purchase cost before discount'
      &gt;&gt;&gt; print('total purchase cost after discount=',h-g)
      Traceback (most recent call last):
      File "&lt;stdin&gt;", line 1, in &lt;module&gt;
      TypeError: unsupported operand type(s) for -: 'str' and 'str'
      &gt;
  </code></pre>