Mainly practicing the connection of arcs, as well as TTR commands and annotations.

Steps:

1. Draw auxiliary lines
2. Draw two circles at both ends, with diameters of 12 and 6 respectively
3. Draw two circles of R21 and R27
4. Draw two circles of R31 and R37
5. Draw two tangent circles of R50 and R55 using TTR command line
6. Use Trim command line to trim off the excess parts
7. Add annotations