mkdir A
chmod 400 A

cp -r A P

The language is:
{ w | w contains at least two a’s, OR exactly two b’s }

Regular Expressions:

Strings with at least two a’s:
(b|a)* a (b|a)* a (b|a)*

Strings with exactly two b’s:
a* b a* b a*

Combined Regular Expression (Union):
((a|b)*a(a|b)*a(a|b)*) | (a*b a*b a*)

Given:
IP Address = 10.20.30.0/25

a) Subnet Mask

A /25 prefix means 25 bits are used for the network.

Subnet Mask = 255.255.255.128

Binary form:
11111111.11111111.11111111.10000000

b) Number of hosts per subnet

Host bits = 32 − 25 = 7 bits

Total IP addresses per subnet = 2⁷ = 128

Usable hosts = 128 − 2 = 126 hosts

(2 addresses are reserved for network and broadcast)

c) Broadcast address

With /25, each subnet block size = 128.

Subnet range:
10.20.30.0 → 10.20.30.127

Network address = 10.20.30.0
Broadcast address = 10.20.30.127

Usable host range:
10.20.30.1 – 10.20.30.126

Final Answers:

Given:
Jobs: J1 = 90K, J2 = 20K, J3 = 50K, J4 = 200K
Blocks: B1 = 50K, B2 = 100K, B3 = 90K, B4 = 200K, B5 = 50K

1) First Fit Method
In First Fit, each job is placed in the first block that is large enough.

Step by step:
J1 = 90K → first block that fits is B2 = 100K
Remaining in B2 = 10K

J2 = 20K → first block that fits is B1 = 50K
Remaining in B1 = 30K

J3 = 50K → first block that fits is B3 = 90K
Remaining in B3 = 40K

J4 = 200K → first block that fits is B4 = 200K
Remaining in B4 = 0K

First Fit Allocation Table:

2) Best Fit Method
In Best Fit, each job is placed in the smallest block that can hold it.

Step by step:
J1 = 90K → best block is B3 = 90K
Remaining in B3 = 0K

J2 = 20K → best block is B1 = 50K
Remaining in B1 = 30K

J3 = 50K → best block is B5 = 50K
Remaining in B5 = 0K

J4 = 200K → best block is B4 = 200K
Remaining in B4 = 0K

Best Fit Allocation Table:

Final Answer:
First Fit allocation:
J1 → B2, J2 → B1, J3 → B3, J4 → B4

Best Fit allocation:
J1 → B3, J2 → B1, J3 → B5, J4 → B4