Answer and Explanation: The farmer has a pure-breeding line of tomato means the farmer has a tomato with genotype FFrrtt while the other line of tomato has genotype ffRRTT.
The cross between these lines gives a F1 generation of heterozygous full, red and axial or FfRrTt.
With an individual of F1 crosses with another individual of F1, the Punnet Square will be:
FfRrTt x FfRrTt
1) Dividing each characteristics, for simplicity:
F f
F FF Ff
f Ff ff
R r
R RR Rr
r Rr rr
T t
T TT Tt
t Tt tt
Analysing Punnett squares, we notice the line wanted (ffrrTT) will be produced, when an individual of F1 generation cross with another individual with the same generation.