Solution:

Given data:
- Width (b) of beam = 250 mm
- Depth (d) of beam = 350 mm
- Area of steel (Ast) = 402 mm²
- Diameter (d) of steel bars = 16 mm
- Effective depth (d') = 314 mm

Percentage of reinforcement is given by the formula:
ρ = (Ast / bd) × 100

Finding the area of cross-section (A) of beam:
A = b × d
A = 250 mm × 350 mm
A = 87500 mm²

Finding the percentage of reinforcement:
ρ = (Ast / bd) × 100
ρ = (402 mm² / (250 mm × 314 mm)) × 100
ρ = 0.512
ρ = 51.2%

Therefore, the answer is (1) 0512.

Explanation:

1. Definition of singly reinforced beam:
A singly reinforced beam is a type of reinforced concrete beam in which reinforcement is provided only on the tension side, while the compression side is left plain.

2. Calculation of area of steel:
Ast = (π / 4) × d² × n
where,
d = diameter of steel bar
n = number of steel bars
Ast = 402 mm² (given)
d = 16 mm (given)
n = 2 (given)

Ast = (π / 4) × (16 mm)² × 2
Ast = 402.12 mm²

3. Calculation of effective depth:
Effective depth (d') is the depth of the beam from the compression face to the centroid of the tension reinforcement. It is given by the formula:
d' = d - (0.5 × cover) - (0.5 × diameter of bar)
where,
d = overall depth of beam
cover = thickness of concrete cover over reinforcement

d' = 314 mm (given)
d = 350 mm (given)
diameter of bar = 16 mm (given)
cover = (d - d') / 2
cover = (350 mm - 314 mm) / 2
cover = 18 mm

d' = d - (0.5 × cover) - (0.5 × diameter of bar)
d' = 350 mm - (0.5 × 18 mm) - (0.5 × 16 mm)
d' = 314 mm

4. Calculation of percentage of reinforcement:
Percentage of reinforcement is the ratio of the area of steel to the total area of the cross-section of the beam multiplied by 100.

ρ = (Ast / bd) × 100
where,
Ast = area of steel
b = width of beam
d = overall depth of beam

ρ = (Ast / bd) × 100
ρ = (402.12 mm² / (250 mm × 314 mm)) × 100
ρ = 0.512
ρ = 51.2%

Hence, the percentage of reinforcement in the given singly reinforced beam is 51.2%.