Data Sufficiency (DS) | Re: Working at a constant rate and by himself, it takes worker U three hou

I am going with D.
ST)If it takes the first worker 180 mins to finish the job and it takes both of the 105/2=52.5 minutes. We can use (xy/x+y) formula to get an answer. 1 is sufficient.
ST2) V=U/.6, U=3, so it takes V, 5 hours, from there we can use the formula from above to get 15/8 as the amount of time it takes them together.

---