Here is a safety play for five out of six tricks. Plenty of entries. The play depends on the spot cards.
Problem 1. J6 opposite AQ7432
Problem 2. J6 opposite AQ7532
In problem one and two, all 3-2 breaks give no problem. THe extra chance comes for 4-1 break. In problem 1, the spot cards are so small, that the only extra chance comes from a singleton king. Start with the A. In problem 2, the presence of the 5 allows you to handle KT84 or KT94 onside, and you can run the Jack on the first round if covered all round, on the next round advance the 6 and run it. If he covers with the 8, your 75 are now equals for a builder against T4.
Afterthought, of all the 4 -1 breaks singleton king is 1/5th, 5.6 % For 8 or 9 to be singleton and only to west, you have 2/5 * 1/2 * 4-1 breaks or the same 5.6%. Can Jannersten be overlooking this since you have to commit to a line of play on problem 2? "Play Safe and Win" Jannersten and Wohlin.