Summing Numbers From Multiple Cells With Text?

I am looking for a formula which will sum numbers with less than symbols in front of them (i.e. they are text cells), and then replace the less than symbol again in the summed cell if initially present. The problem is that not every cell contains a < symbol, some of them are just numbers, and not every column contains a < symbol either.

e.g. I am looking for a formula which if entered in row 5 of this example would give these answers.

A
B
C
D

1
<0.001
<0.1
0.2
<0.01

2
<0.0001
0.1
0.2
<0.1

3
<0.0001
<0.2
0.2
<0.1

4
<0.001
<0.1
0.2
<0.01

5
<0.0022
<0.5
0.8
<0.22