Ruby On Rails : How to Put Space Inside tag in Rails With Multiple Variable Values To Render

I have a form which display the Full name of the customer in read only mode which look like bellow

What I require is to have a white space in between First name, Middle name and Last name. I tried many times with different code but it failed, I am giving bellow my code, what to do ?

<div class="form-group">
          <label class="col-md-4 control-label" for="textinput">Customer Name :</label>  
          <div class="col-md-4">
          <b><input id="textinput" name="textinput" type="text" placeholder="placeholder" class="form-control input-md" value = <%= @lastcustomer.firstname%><%= @lastcustomer.middlename %><%= @lastcustomer.lastname %>  readonly> </b>
   </div>
</div>