How many significant digits are in 0.006010 ?

Someone answer this check out the image!

Given: circle o, cd is diameter, chord ab || cd. arc ab = 74°, find arc ca.

The figure shows triangle def and line segment bc, which is parallel to ef: triangle def has a point b on side de and point c on side df. the line bc is parallel to the line ef. part a: is triangle def similar to triangle dbc? explain using what you know about triangle similarity. part b: which line segment on triangle dbc corresponds to line segment ef? explain your answer. part c: which angle on triangle dbc corresponds to angle f? explain your answer. asap