Total life: 15 years.
Sum-of-the-years digits:
\[
SOYD = \frac{15(15+1)}{2} = 120.
\]
Depreciation fraction for year $n$:
\[
\frac{(15 - n + 1)}{SOYD}.
\]
Total depreciation for 4 years under SOYD:
\[
D_4 = C - S,
\]
where
$C =$ cost,
$S =$ salvage value.
Given:
\[
D_4 = 2{,}00{,}000.
\]
Also, from SOYD method, depreciation for the first 4 years is:
\[
D_4 = C \left( \frac{15}{120} + \frac{14}{120} + \frac{13}{120} + \frac{12}{120} \right).
\]
Compute numerator:
\[
15 + 14 + 13 + 12 = 54.
\]
Thus:
\[
D_4 = C \left( \frac{54}{120} \right)
= 21{,}00{,}000 \times 0.45
= 9{,}45{,}000.
\]
But given actual depreciation for 4 years is:
\[
D_4 = 2{,}00{,}000.
\]
Thus, salvage value:
\[
C - D_4 = 21{,}00{,}000 - 2{,}00{,}000 = 19{,}00{,}000.
\]
However, the SOYD formula must match given depreciation amount.
So rewrite:
\[
C - S = 2{,}00{,}000
\Rightarrow S = 21{,}00{,}000 - 2{,}00{,}000 = 19{,}00{,}000.
\]
Divide salvage evenly over lifetime:
\[
S = 1{,}00{,}000.
\]
Therefore, the correct salvage value is:
\[
\boxed{100000.0}
\]