How to compare acidity in the following aniline derivatives?

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Let the simplest one be a), ortho be b), meta be c) and para be d).
I have confusion between ortho and meta. How to compare their acidity?




Taking the case of ortho and meta in which you have confusion: 


The acidity of aniline will increase if there is a electron donating group in the compound to stabilise the conjugate positive acid formed.


Since OMe is shows +R and -I effect, it is a net electron donating group as +R effect generally dominates over -I.So in case of ortho it is able to show electron donating nature due to +R effect which makes it more basic than the meta isomer which shows electron withdrawing effect due to only -I effect as +R effect will not affect from meta position.


 2

According to [source](http://sites.chem.colostate.edu/diverdi/all_courses/CRC%20reference%20data/dissociation%20constants%20of%20organic%20acids%20and%20bases.pdf) the pKa values (of the conjugate acid) are:



```
compound            °C    pKa
Aniline             25    4.87
2-Methoxyaniline    25    4.53
3-Methoxyaniline    25    4.20
4-Methoxyaniline    25    5.36

```

 0