Step 1) Create a rectangle centered at the origin with a height of 20 and width of 30:

Step 2) add an arc as shown. Make sure it’s dimensioned :

Step 3) Now the bottom:

 

Step 4) Extrude the shape by 25MM:

Step 5)  un-hide sketch 1

Step 6)

Go into sketch 1 and create  2 MM offset on the top arc and on the bottom arc, then connect their endspoints with lines :

Step 7)

Final Result