Eek, planning...

[TioMio]

What about this (about solution to 4)?

$$c
$$ ---------------
$$ | . 2 . 4 . X .
$$ | O O 1 . . X .
$$ | . O . O O X .
$$ | 3 O . X . X .
$$ | . X X . X . .
$$ | . . . . . . .

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[go]$$c
$$ ---------------
$$ | . 2 . 4 . X .
$$ | O O 1 . . X .
$$ | . O . O O X .
$$ | 3 O . X . X .
$$ | . X X . X . .
$$ | . . . . . . .[/go]

$$c
$$ ---------------
$$ | . 2 . 4 . X .
$$ | O O 1 7 8 X .
$$ | . O 5 O O X .
$$ | 3 O 6 X . X .
$$ | . X X . X . .
$$ | . . . . . . .

Click Here To Show Diagram Code

[go]$$c
$$ ---------------
$$ | . 2 . 4 . X .
$$ | O O 1 7 8 X .
$$ | . O 5 O O X .
$$ | 3 O 6 X . X .
$$ | . X X . X . .
$$ | . . . . . . .[/go]

$$c
$$ ---------------
$$ | . 2 . 4 . X .
$$ | O O 1 8 7 X .
$$ | . O 6 O O X .
$$ | 3 O 5 X . X .
$$ | . X X . X . .
$$ | . . . . . . .

Click Here To Show Diagram Code

[go]$$c
$$ ---------------
$$ | . 2 . 4 . X .
$$ | O O 1 8 7 X .
$$ | . O 6 O O X .
$$ | 3 O 5 X . X .
$$ | . X X . X . .
$$ | . . . . . . .[/go]

Then 1 at c18 doesn't seem to work. Though perhaps 4 could be somewhere else to maximize profit. But I just proofread this 4.