Answer from cs61c-ar (Albert Chung 15826273) for Question 2
The instruction add requres the registers $t0, which are loaded in too late for the add instruction.  Thus, the hardware can use forwarding to help the situation, but even this might be too late.  Then, the programmer can reorder the code so that the next line of instruction after the lw can be something else and call the add instruction a few lines later.